The invention relates to expandable structures, which, in use, are deployed in interior body regions of humans and other animals.
The deployment of expandable structures, sometimes generically called xe2x80x9cballoons,xe2x80x9d into cancellous bone is known. For example, U.S. Pat. Nos. 4,969,888 and 5,108,404 disclose apparatus and methods using expandable structures to compact cancellous bone for the fixation of fractures or other osteoporotic and non-osteoporotic conditions of human and animal bones.
In these and other clinical indications, it is desirable to use tissue insertion and deployment tools that are small, so that access to the targeted tissue site can be achieved using minimally invasive procedures. Still, it is also desirable to deploy structures that, in use within the targeted tissue site, are capable of assuming enlarged, durable shapes, so that cortical bone can be displaced in a desired manner and/or large cavities can be created in cancellous bone without over-expansion, puncture, and/or abrasion of the structure.
There is a need to meet the demand for small insertion tools without conflicting with the objective to deploy large expandable structures.
The invention provides systems and methods that permit expandable, large, durable structures to be deployed through small, minimally invasive accesses.
One aspect of the invention provides a tool for treating bone. The tool comprises a structure having opposite ends spaced along an axis. The structure is adapted to be inserted into bone and undergo expansion outwardly about the axis in cancellous bone and/or against cortical bone. The tool includes a wrapping mechanism coupled to the structure. The wrapping mechanism wraps the structure inwardly about the axis, to reduce its outside diameter to facilitate its insertion into bone.
In one embodiment, the wrapping mechanism is operable to impart a force to stretch the structure along the axis.
In one embodiment, the wrapping mechanism is operable to impart a force to stretch the structure along the axis while wrapping the structure inwardly about the axis.
In one embodiment, the wrapping mechanism is operable to affect differential rotation of one end of the structure about the axis relative to the other end, thereby wrapping the structure inwardly about is axis.
In one embodiment, the opposite ends of the structure comprise a proximal end and a distal end. In one arrangement, the wrapping mechanism affects differential rotation of the distal end relative to the proximal end. In another arrangement, the wrapping mechanism affects differential rotation of the proximal end relative to the distal end.
In one embodiment, a proximal end of the structure is carried by a catheter tube. In this arrangement, the wrapping mechanism is coupled to a distal end of the structure to rotate the distal structure end about the axis while the proximal structure end is held substantially free of rotation by the catheter tube.
In one embodiment the wrapping mechanism includes an actuator carried on the proximal end of a catheter tube, the distal end of which carries the structure.
In one embodiment, a proximal end of the structure is carried at the distal end of a catheter tube. The wrapping mechanism includes a stylet rotatable within the catheter tube having a far end coupled to the distal end of the structure. In this arrangement, an actuator on the proximal end of the catheter tube is coupled to a near end of the stylet to rotate the stylet within the catheter tube. Rotation of the stylet, in turn, affects rotation of the distal end of the structure while the proximal end of the structure is held substantially free of rotation by the distal end of the catheter tube.
In one embodiment, the wrapping mechanism includes an element that imposes a force to resist unwrapping of the structure.
In one embodiment, the structure includes material that, during expansion in cancellous bone, applies a force capable of moving fractured cortical bone.
In one embodiment, the structure includes material to constrain expansion in cancellous bone.
In one embodiment, the structure includes S material that expands directly against cortical bone to displace the cortical bone in a desired direction.
In one embodiment, the structure includes an elastomer material having a region preformed with a normally expanded shape outside bone.
In one embodiment, the structure comprises a stop which prevents and/or inhibits the structure from being advanced into the bone beyond a predetermined depth.
Another aspect of the invention provides a method for treating bone. The method provides a structure having opposite ends spaced along an axis. The structure is adapted to undergo expansion outwardly about the axis. The structure possesses a normally unwrapped condition having an outside diameter. The method places the structure in a wrapped condition by wrapping the structure inwardly about the axis to reduce the outside diameter. The method inserts the structure, while in the wrapped condition, into bone. The structure returns to the unwrapped condition inside bone and causes expansion of the structure in cancellous bone.
In one embodiment, the method includes the step of introducing a material into the bone.
In one embodiment, the step of expansion moves cortical bone.
In one embodiment, the method includes, after the expansion step, the step of reducing the size of the structure for removal from the bone. In one arrangement, the reducing step includes placing the structure in the wrapped condition.
In an alternate embodiment, the method comprises reducing the size of the structure for removal from the bone. In one arrangement, the reducing step includes placing the structure in the wrapped condition.
In one embodiment, the wrapping step includes causing differential rotation of one end of the structure about the axis relative to the other end.
Features and advantages of the inventions are set forth in the following Description and Drawings, as well as in the appended claims.